In 1936, the geneticist Richard Goldschmidt (1878–1958) was forced to relinquish his position as director at the Kaiser Wilhelm Institute (KWI) for Biology in Berlin Dahlem due to National Socialist anti-Semitism. His emigration to the United States at the age of nearly fifty-eight meant leaving behind excellent working conditions, his editorship of important journals, and a highly influential position in German-language genetics. He was never able to achieve a comparable status in the United States. His position at the KWI in Berlin was assumed by Alfred Kühn (1885–1968). Goldschmidt and Kühn were representatives of different genetic concepts; the forced personnel change thus also meant a change on the scientific level.

Toward the end of World War II, Kühn collaborated with the biochemist Adolf Butenandt (1903–1991) to develop, supported by their staff, a model of the relation between gene and character. This model is valid even today as part of the “one gene-one enzyme hypothesis” and thus constitutes an important element of molecular genetics. The model concurred with the “theory of the gene” developed after 1914 by the school of Thomas Hunt Morgan (1866–1945), which prevailed in further research including the mapping of the human genome. According to this theory, genes are corpuscular units, lined up in the chromosome like pearls on a string, each of which can be defined precisely with respect to their molecular size. Through enzymes, these units determine the hereditary characters of the cell.